Mechanical stoker



Feb. 21, 1928.

W. M. DUNCAN MECHANICAL STOKER Filed April 13, 1925 2 Sheets-sneer. l

MM. Dunc/w ATTORNEYS Patented Feb. 21, 1928.

UNITED STATES WILLIAM M. DUNCAN, F ALTON, ILLINOIS MECHANICAL STOKER.

Application filed April 13, 1925. Serial No. 22,593.

This invention relates to improvements in mechanical stokers and more particularly to means for creating draft and inducing ready ignition of the fuel at that portion of a traveling chain grate where said fuel is discharged in agreen condition onto said traveling chain grate from a hopper.

Mechanical stokers of the type disclosed herein usually comprise an endless traveling chain grate which surrounds one or more draft boxes and a hopper adjacent to one end of said traveling chain grate from which fuel is discharged onto said traveling chain rate. In the operation of a mechanical stoker of the type suggested, fuel. is deposited on the upper flight of the traveling chain grate and said fuel is carried along by the traveling chain grate above the draft box or boxes. During the passage of the bed of fuel above the draft box or boxes, draft is caused to flow through said bed of fuel whereby ignition and combustion of said fuel is induced.

In the operation of a mechanical stolrer of l the type disclosed herein it has been found that some fuel, for instance, fine co to known as coke breeze, anthracite coal and other fuel will not ignite readily. In other words, this fuel must travel a short distance Within the furnace before it will ignite. A mechanical stoker attains its greatest efiiciency when the fuel is ignited immediately upon being deposited upon the traveling chain grate and I have therefore devised the stocker disclosed in the present application which is so constructed and arranged that suction is created above the surface of the bed of burning fuel which suction draws flame and .hot gases toward the point where the green fuel is de' posited on the, traveling grate. In thismanner draft is created and ignition of the fuel is induced immediately as said fuel is cleposited on the traveling grate and the efiiciency of the stoker is thereby greatly increased.

Another object of my invention is to produce a mechanical stoker which is provided with a single draft boxarranged longitudinally of the traveling chain grate forming a part of said mechanical stoker.

With the foregoing and other objects in view, the invention comprises the novel construction, combination and arrangement of parts hereinafter more specifically described and illustrated in the accompanying drawings, wherein is shown the preferred emboditom plates-15. the loose upon the plates 15 and ashes are permitted to ment of the invention. However, it is to be understood that the invention comprehends changes variations and modifications which come within thescope of the claims hereunto appended.

Fig. I is a longitudinal section of a mechanical stoker embodying the features of this invention.

I Fig. II is a cross-section on line II-II of Fig. I. v

Fig. III is a horizontal section on line III-III of Fig. I. 1

Fig. IV is a cross-section on line I V-IV of Fig. I.

A designates an endless traveling chain grate arranged between theside walls 1 of a furnace and supported partly by bars 2 located immediately beneath the fuel supportmg portion of the grate and partly hybars 3 on which the lower portion of the grate travels. Additional supports are formed by a roller 4 at the rearof the grate and a suitable number of sprockets wheels 5 secured to an operating shaft 6 at the front of the grat". The shaft 6 may be driven in any suitable manner to cause the upper portion of the grate to travel in the directionindicated bv the feathered arrows in Fig. I. The fuel is suppliedthrougha hopper 7 at the front of the grate andthe ashes are discharged by gravity at therear of said grate.

Side frames 8 located at the opposite S'flts of the grate support beam 9 arran ed transversely of the grate. said beams 9 being co..- nectedto said side frames in any convenient manner. Interposed between the upper and lower flights of the traveling chain grate is a draft box 10. said draft box comprising end walls 11 and 12 which are secured to the side frames 8 andcertain of the beams 9. The lower margin of each of the end walls 11 and 12 is provided with a recess 13 open at the bottom to receive a loose sealing bar 14. The bottom of the draft box is formed by inde' pendently yieldable plates 15 arranged longitudinally of the grate upon the traveling lower portion thereof. Each of these loosely mounted plates is turned upwardly at its opposite ends to form abutments 16 which engage tubes 17 to prevent longitudinal displacement of said plates. To prevent leak age of draft between the lower margins of the endwalls 11 and 12 and the yieldingbotsealing bars 14 rest accumulate at these sealing bars as suggested in Fig. I. Also to prevent leakage of draft at the sides of the draft boxes I employ 7. bars 18 which are secured to the frames 8 in a manner to provide recesses 19 adapted to receive legs of angular bars 20 which angular bars rest upon certain of the plates and are loosely mounted in said recesses 19 (Fig. IV). Ashes are pern'iitted to accumulate adjacent to the angular bars 20 also .to produce ash seals at these points.

Arranged in the upper portion of the draft boxes 10 is a plurality of fixed inclined walls 21 and associated with each of said inclined walls is a hinged damper 22. The inclined walls 21 are so arranged with respect to the associated hinged dampers that a plurality of compartments may be provided in the upper portion of the draft boxes and said pivoted dampers are capable of independent manipulation so that independent regulation of draft through the various,compartments is possible. Because of the arrangement just described, it is apparent that a single draft box is utilized with the stoker disclosed herein which draft box extends longitudinally of the traveling chain grate of said stoker and that the upper portion of this draft box is divided into draft zones which are provided with independent draft regulators controlling the flow of draft through the respective zones. My improved stoker may be provided with openings 8 in one of the side frames 8 allowing air to flow into and through the draft box 10.

By referring now to Fig. I of the drawing, it will be seen that the ignition arch 23 of the furnace is spaced apart a slight distance in a horizontal direction from the hopper 7 to provide an opening 24. Arranged partly within the opening 24 and partly thereabove is my improved means forinducing the ready ignition of fuel immediately after it has been deposited on the traveling chain grate of the stoker, which means, broadly speaking comprises a flue B, one open end of which is arranged immediately above the discharge end of the hopper 7 and the other end portion of which extends some distance above the stoker. By referring to the lowermost end portion of the flue B it will be notedthat I employ an elongated hollow member 25 preferably rectangular in horizontal section which is open at thetop and bottom. The hollow member 25 is arranged transversely of the stoker and the forward wall of said member 25 constitutes a portion of the rearmost wall of the hopper 7 a portion of said forward wall of said member 25 being inclined to correspond to the inclination of the wall 7' of the hopper 7 whereby the inclined discharge portion of the hopper 7 is produced. Extended upward from the hollow member 25 is a hollow member 26, preferably formed of sheet metal and being in horizontal section of approximately the same shape and the same dimensions as the member 25, the lower edge portion of said member 26 being secured in any suitable manner to the upper edge portion of the member 25. The member 26 is provided with inclined top walls 27 which terminate at an opening in which is arranged a vertically positioned conductor 28. The vertically positioned conductor 28 is in communication with the interior of the member 26, as shown in Fig. I, and said conductor is provided with an upwardly flared portion 28 which is surmounted by a portion 29 having a vertical annular wall of greater diameter than the lower portion of said conductor.

31 designates a vertical conductor or flue preferably formed of sheet metal which is associated with the conductor 28. The conductor 31 is of such'diameter that its lower end portion fits into the enlarged upper portion of the conductor 28. the annular walls of said conductors 28 and 31 fitting together closely enough to prevent the free escape of draft through the joint therebetween. The telescoping arrangement just described provides a slip joint which permits of the conductor 28 and the elements associated therewith being moved vertically relative to the conductor 31. The conductor 31 is extended upwardly from the stoker a sufficient distance to provide for the creation of draft within the combustion chamber of the furnace.

To provide for vertical movement of the member 26 together with its associated elements I arrange laterally extended flanges 82 at the upper edges of the side frames 8 of the stoker (Fig. 11). Secured to the member 26 adjacent to said flanges 32 are brackets 33, said brackets being riveted or otherwise secured to said member 26 so that they are movable therewith. The brackets are provided with L-shaped members 34: having horizontal legs which are arranged immediately above the flanges 32 as shown in Fig. II, said horizontal legs being each provided with an internally threaded aperture formed therethrough. Extended through the internally threaded apertures of the L- shaped members 34 are threaded. members 35. The threaded members 35 are provided with non-circular headsto facilitate the manipulation thereof and the opposite ends of said threaded members bear against the top faces of the flanges 82. Due to the fact that the L-shaped members 34: secured through the medium of the brackets to the member 26 and because the threaded members 35 contact with the flanges 32 on the rigid side frames 8, it is apparent that by rotating the threaded members 35 the member 26 may be raised or lowered according to the direction of rotation of said threaded members.

1 midway between the top and bottom edges 0 of said wall of said member 25. 40 designates a plurality of holding devices which are adapted tosupport a plurality of ignition blocks 41 and to securesaid ignition blocks to the hollow member 25 so that they are movable therewith. By referring to Fig. III'it will be seen that a plurality of holding devices are arranged side by side longitudinally of the member 25 and that eachof said holding devices supports a block 41 ofrefractory material whereby a continuous Wallis provided which because of the nature of the material of which it is formedwillradiate heat and thereby improve the combustion of the fuel adjacent to said wall. Each of the holding devices is providedwith a pair of oppositely disposed vertical flanges 42 which are, adapted to be extended into vertically arranged grooves 43 in the side faces of the blocks 41. The holding devices are each provided with a horizontal flange 44 upon'which a portion of the bottom face of the associated block 41 rests (Fig. I). Formed on the holding devices are T-shaped extensions 44' which are arranged vertically and adapted to be extended into the T-shaped vertical slots in the comparatively thickportionof the forward wall of the member 25 asshown in Fig. III.

To assemble the member 25, holding devices 40 and blocks 41, the T-shaped portions 44 on the holding devices are arranged in alinement with the T-shaped slots in the relatively thick wall portion of the member 25. The T-shaped portions 44 are then moved downwardly within said T-shaped grooves until the lower faces of the T-.

shaped portions contact with the shoulders 39. The blocks 41 are then positioned above the holding devices so that the vertical flanges 42 on said holding devices are in alinement with the vertical grooves 43 in said blocks after which said blocks are moved downwardly to cause the vertical flanges on the holding devices to move into the vertical grooves in the blocks. The downward movement of the blocks 41 relative to the holding device is arrested when portions of the lower faces of the blocks contact with the flanges 44 of the holding devices. It is apparent from the foregoing that the elements mentioned are firmly connected together and that in the event the member 25 was moved vertically by the adjusting devices already described, said holdingdevices and blocks would move with said member 25.

Secured to the member 25 is a leveling plate 45 which is intended to regulate the height of the bed of fuel being deposited of the flue B, that is the members 25 and 26 andthe associated parts, are movable vertically: However, it is not desirable that the conductor 31 be moved with the parts just mentioned. I therefore secure the conductor 31'to a fixed support such as the one illustrated in Fig. I and designated by the reference character 46. The conductor 31 may be fixed to the support 46 infany convenient manner and because of the slip joint between the lower portion of the conductor 31 and the upper portion 29 of the member 28, the lower portlon of the flue B may be moved vertically without moving the conductor 31.

In the operation of the mechanical stoker disclosed herein the endless traveling chain grateiscaused to travel in the direction indicated by the feathered arrows in Fig. I and draft is forced by suitable means "into the draft box 10 and then through the bed of burning fuel on the upper flight of the traveling gate. At the same time the flue B will create an auxiliary natural draft within the combustion chamber of the furnace which will draw flame and hotgases in the direction indicated by the unfeathered arrows in Fig. I. The point at which the natural draft escapes from the combustion chamber is immediately above the point where the green fuel is deposited on the traveling chain grate, the bottom oft-he flue being formed by the leveling members 45. Consequently the flame and hot gases will be drawn to that point. The forward move ment of the flame and hot gases as described results in the promotion of surface ignition and in the ready ignition of the green fuel deposited on the grate, and also this forward movementof flame and hot gases results in aheating of the heat radiating blocks 41, all of which tends to greatly improve the combustion of the fuel.

While I. have shown a comparatively. high flue B to create draft within the combustion chamber of the furnace, I may dispense with this high flue as an outlet above the point where the green fuel is deposited on the grate, for the pressure within the combustion chamber in some cases may be sufficient to cause a movement of flame and hot gases toward the forward end of the stoker. Also I may instead of creating a natural draft within the combustion chamber of the furnace employ artificial means for creating the auxiliary draft.

I claim:

l. A furnace provided with a mechanical Stoker comprising an endless chain grate arranged within the combustion chamber of said furnace, means whereby fuel is deposited on said endless chain grate, means whereby draft is caused to flow through the bedv of fuel on said endless chain grate, and means for creating suction within the combustion chamber of the furnace and above the bed of fuel on the endless chain grate whereby flame and hot gases are drawn toward the point where the green fuel is de posited on said endless chain grate, the last mentioned means comprising a flue provided with a lower portionhaving an open lower end located adjacent to and immediately above the point where the fuel is deposited on said endless chain grate, and said lower portion being telescoped with and adjustable relative to the upper portion of the flue.

2. A furnace provided with a mechanical stoker comprising an endless chain grate arranged within the combustion chamber of said furnace, means whereby fuel is deposited on said endless chain grate, means whereby draft is caused to flow through the bed of fuel on said endless chain grate, means for creating suction within the combustion chamber of the furnace whereby flame and hot gases are drawn toward the point where the fuel is deposited on said endless chain grate, the last mentioned means comprising a flue communicating with said combustion chamber at a point adjacent to and above said point where said fuel is deposited on said endless chain grate, and a vertically adjustable leveling member forming the bottom of said fine and adapted to regulate the height of the bed of fuel on said endless chain grate.

3. A furnace provided with a mechanical stoker comprising an endless chain grate arranged within the combustion chamber of said furnace, means whereby fuel is deposited on said endless chain grate, means whereby draft is caused to flow through the bed of fuel on said endless chain grate, means for creating suction within the combustion chamber of the furnace whereby flame and hot gases are drawn toward the point where the green fuel is deposited onthe. endless chain grate, the last mentioned means comprising a vertically adjustable flue one end of which is located adjacent to and immediately above said point where said fuel is deposited on said endless chain grate, and a leveling plate secured to said fine and ad ited on said endless chain grate, means whereby draft is caused to flow through the bed of fuel on said endless chain grate, means for creating suction within the combustion chamber of the furnace whereby flame and hot gases are drawn toward the point where the fuel is deposited on said endless chain grate, the last mentioned means comprising a vertically adjustable flue one end of which is located adjacent to and immediately above said point where said fuel is deposited on said endless chain grate, a leveling plate secured to and movable with said flue whereby the height of the bed of fuel deposited on said chain grate may be regulated, and a pluralitv of heat radiating blocks movable with said flue and said leveling plate.

In testimony that I claim the foregoing I hereunto afliX my signature.

WILLIAM M. DUNCAN. 

